High-solids environments

In order to simplify the overall picture, the environments in which biodegradation occurs are divided into two environments, aerobic, where oxygen is available, and anaerobic, where no oxygen is present. These two can in turn be subdivided into aquatic and high solids environments. 

A broader, more generie name for fuel eells operating at the temperatures described in this seetion would be "ceramie" fuel eells. The electrolyte of these eells is made primarily from solid ceramie material to smvive the high temperature environment. The eleetrolyte of present SOFCs is oxygen ion conducting. Ceramic cells eould also be proton eonducting. 

It is commonplace to assume a form of the Gibbs energy function which excludes the pressure variable for solid-state phase transformations, as the magnitude of the PAV term is small at atmospheric pressures. This is of course not the case in geological systems, or if laboratory experiments are deliberately geared to high-pressure environments. Klement and Jayaraman (1966) provide a good review of the data available at the time when some of the earliest CALPHAD-type calculations were made (Kaufman and Bernstein 1970, Kaufman 1974). Much work was also carried out on specific alloy systems such as Fe-C (Hilliard 1963) and the Tl-In system (Meyerhoff and Smith 1963). 

Inflammability or Flammability (latter is preferred in modern usage). The ease with which a material (gas, liquid or solid) will ignite, either spontaneously (pyrophoric), from exposure to a high-temperature environment (autoignition), or to a spark or open flame. It also involves the rate of spreading of a flame once it has started. The more readily ignition occurs, the more flammable the material less easily ignited materials are said to be combustible, but the line of demarcation is often indefinite, and depends on the state of subdivision of the material as well as on its chemical nature... 

The rate of sampling with piezoelectric sensors is limited by their physical characteristics and present technology to the millisecond range for applications in the liquid phase. The technique is versatile in that it can be used in a variety of locations. The solid state electronics necessary to operate the piezoelectric sensor are easily miniaturized, and data can be recorded continuously or periodically. A small computer with a reasonable memory could easily record data over long times. There may be some problems in deep-sea locations, simply because of the complications in packaging the sensor for high-pressure environments, although this problem may be surmountable. 

Therefore, the solid sorbent should ideally have a low affinity to water, a characteristic easily met by the porous organic polymers. In contrast, the carbon-based sorbents and molecular sieves as well as some inorganic sorbents show a comparatively high uptake of water. If such sorbents are used in high-humidity environments special measures have to be employed to remove water during or after sampling. Possible methods are ... 

One of the important characteristics of gas-solid multiphase flows is concerned with the electrostatic effect. Particles can be charged by surface contact in a collision, by corona charging and scattering in an ionized gas, by thermionic emission in a high-temperature environment, and by other charging mechanisms such as colloidal propulsion... 

When solid particles are exposed to a high-temperature environment, typically for T > 1,000 K, charging by thermal electrification becomes important. The electrons inside the solid can acquire the energy from the high-temperature field and be freed by overcoming the energy barrier or the work function. By losing electrons in such a thermionic emission process, the particles are thermally electrified. 

In the slip-casting process the ceramic powder is suspended in a fluid vehicle, usually water. The suspension, or slip , has a high solids content, typically 50vol.%, and the individual particles are fine, usually less than 10 /mi. Deflocculants, which modify the electrical environment of each particle so that they repel one another, are added to the slip. The fineness of the powder and consequent high surface area ensure that electrostatic forces dominate gravity forces so that settling does not occur. When exceptionally heavy powder particles... 

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